Propagate control flow to bound double colon expressions

"Unused expression" should be reported on unused double colon expressions, this
is postponed

 #KT-12551 Open

compiler/testData/diagnostics/tests/callableReference/bound/controlFlow.kt

@@ -0,0 +1,23 @@
+fun unusedExpression(s: String) {
+    // TODO: report UNUSED_EXPRESSION (KT-12551)
+    s::hashCode
+    s::class
+}
+
+fun noUnusedParameter(s: String): Int {
+    val f = s::hashCode
+    return f()
+}
+
+fun unreachableCode(): Int {
+    (if (true) return 1 else return 0)::toString
+    <!UNREACHABLE_CODE!>return 0<!>
+}
+
+fun unreachableCodeInLoop(): Int {
+    while (true) {
+        (break)::toString
+        <!UNREACHABLE_CODE!>return 1<!>
+    }
+    return 2
+}